Reason

"Southpaw" originated from the American sport of baseball, usually refering to a left hand pitcher. It comes from the practice of arranging the diamond (the baseball "field") with the batter facing east to avoid the afternoon sun. A left-handed pitcher facing west would therefore have his pitching arm toward the south of the diamond.

Sweetmeat required a bit of research.  The first part was easy.

Sweetmeat -- meaning candy -- is an archaic word still commonly used by English speakers in the Middle East and India. In the rest of the English-speaking world -- Britain, Canada, US, Australia -- the preferred term has become "sweets", a shortening of sweetmeats that first appeared in the 14th century.

Because I was only vaguely familiar with "sweetmeat", I dug further.

According to a 2008 blog written by the staff of the OED at Oxford University Press, the origin of sweetmeat is obscure. Sweet comes from the Old English swête meaning sweet. In sweetmeat, like mincemeat, the "meat" appears to have retained its original, broader and generic meaning of "food". In the Old Germanic languages, meat signified “food.” Meat and mete (out) “measure out, apportion” are related: meat referred to the food cut for the eater (or perhaps for sacrificial purposes).

So "sweetmeat" was sweet food, later shortened in the West to "sweets" or candy.